1. Field of the Invention
This invention relates generally to cargo containers capable of withstanding and containing explosions therein. More specifically, the invention is directed at such containers that are also sufficiently lightweight such that it is not cost prohibitive to use them on aircraft.
2. Description of Related Art
In the airline industry, containment devices are commonly referred to as Unit Load Devices (ULDs). Explosion resistant containment devices are known as Hardened Unit Load Devices (HULDs). The specifications (weight, size, shape) for either type of ULD have been partially standardized by regulatory requirements and on account of practical concerns. The odd shape of the containers, with its sloped surfaces is designed so that the ULD fits into the aircraft's fuselage specifically.
Current ULD's are typically constructed of lightweight aluminum or other thin metal or composite materials that provide no protection against an explosive blast and becomes shrapnel during even a small explosion.
A problematic drawback of conventional HULDs or explosion resistant containment devices has been that they are generally heavier than conventional ULDs and cargo containers with thicker walls. While benefits provided by HULDs, including enhanced safety and preventing damage to other cargo, are highly desirable the increase in weight can be cost prohibitive in an already struggling industry.
With airlines already struggling to stay in business and the average traveler for pleasure unwilling to spend more than a certain amount to fly, this increase in weight for safer blast resistant containers can be cost prohibitive. It is unfortunate that the cost of this important safety measure should come at a price so high that it is not implemented. There is a need for a lighter weight, less expensive explosion resistant containment device than those presently available.
When an explosion occurs there is initially a high magnitude shock wave for a short duration followed by lower magnitude, more uniform waves that last much longer. A blast-resistant container must be able to survive both stages and both types of waves. Even the second stage of lower magnitude waves are generally several times atmospheric pressure which is more than the conventional ULD can withstand.
Known techniques for modifying cargo containers to deal with explosions in the fuselage include the venting method, the rigid confining method, and frameless designs. The venting method involves allowing an explosive to penetrate a wall of the fuselage to vent shock waves and high pressures outside the plane. Obviously, controlling the destruction is less ideal than preventing it altogether and is costly due to the damage suffered by the plane. The rigid confining method involves thick, energy-absorbing panels mounted on a rigid frame. The thick panels are focused on absorbing high energy produced during the explosion but the more relevant factor is high stress. Thick panels and a rigid frame can exacerbate concentration of stress at the edges and may be unable to appropriately reduce or redistribute bending stresses. In frameless designs the container is designed to flex, bend, and otherwise deform during a blast. One problem that remains is how to connect the panels to provide structural integrity and how to incorporate a latching mechanism doesn't disproportionately weight down the container.
There is a need for a heat and explosion resistant cargo/baggage container having a panel connection design and latching mechanism that does not undermine the blast resistant nature of the container's panels. The unique door latching/locking mechanism as shown and described herein is easier and faster to operate as compared to the designs incorporated in older Hardened Unit Load Devices (HULDs). One of these older latching/locking mechanism designs consisted of a pair of opposing hook-shape rails and required other tensioning devices (e.g. straps) to make it secure.
Further, there exists a need for a blast resistant cargo/baggage container for aircraft that weighs approximately the same as or less than a conventional, non-hardened, non-blast resistant container. It would be desirable for the walls of the container to be formed of lighter weight materials capable of protecting against an explosive without rupturing and without concentrating too much stress at the edges and near the latch. The present invention meets these needs.